Topical medications, or drugs applied to the surface of the skin, are available in gel, foam, ointment, cream and other bases. Topical medications generally operate by passing through the surface of the skin, through the uppermost layer of skin, or epidermis, and into the underlying skin layer, the dermis. Some topical medications may penetrate even deeper, into the tissue fluid underlying the dermis, producing a therapeutic effect in a greater distributed area around the spot of application, or even producing a more systemic, or body-wide, effect.
In addition to the potency of a topical drug, other factors also contribute to the effectiveness of a drug. Increasing the rate of penetration, characterized as the amount of drug penetrating into the skin per unit of time, also lessens the time it takes for an effective amount of the drug to become present in the skin. Sustaining the rate of penetration after initial application ensures that the drug is still actively passing through the skin long after it is applied, contributing to the length of time a drug may be effective before needing reapplication. Consequently, improving the initial penetration rate and sustaining a high rate of penetration long after application can yield a higher cumulative amount of drug penetration.
Moreover, the depth of penetration is also important, since a more widespread or systemic effect can often be achieved the deeper a drug penetrates into the skin. Further, the distribution of the drug into the skin, or amount of drug retained in a particular skin layer (as a percentage of applied dose), is an indicator of how much drug is present in the layer in which it is most therapeutic.
As topical drugs can be expensive, it would be of particular benefit to increase the effectiveness of topically applied medications. Generally, once a drug is applied to the skin, the amount of drug passing through the skin increases from zero to a peak rate relatively quickly, then tends to drop off as time elapses. Increasing initial penetration rate and sustaining a steady penetration rate for a longer time after application would be beneficial.
Luxíq® is the brand name of a foam-based topical corticosteroid formulation of the prescription drug betamethasone valerate. After applying a dose of Luxíq to skin pre-treated with a 1,2-propylene glycol and mineral oil solution, initial penetration rates of the drug through the surface of the skin are significantly lower compared to a control application of the drug with no skin pre-treatment. However, the sustained penetration rate of the skin pre-treated with the prior art solution shows improvement over that of untreated skin, with a smaller decrease in penetration rate over several hours.
With the pre-treated skin, the cumulative amount of the drug penetrating through the skin over time shows slight improvement over that of the control drug application. Distribution of the drug in the epidermis, as a percentage of applied dosage, also shows slight improvement. However, distribution of the drug in the dermis and tissue fluid shows a marked decrease and little change, respectively. As Luxíq is most therapeutic in the dermis, and pre-treatment of the skin with the prior art solution has been shown to hinder, and therefore not significantly improve, penetration to this layer, a more effective skin pre-treatment composition is desired.
Transdermal patches are medicated patches applied to the skin having treatments intended to pass through the skin to have a therapeutic or preventive effect, including patches for motion sickness, heart medication, contraception, asthma, and smoking cessation. Many transdermal patches would benefit from more rapid and longer sustained effectiveness. In the case of heart patients or asthma patients, it may be critical for the therapeutic effect of the patch to be more immediate. Maintaining more constant drug levels in the skin would be greatly beneficial to many applications, including motion sickness, contraception and smoking cessation treatments.
Sunscreens also would benefit from quicker penetration, a higher rate of penetration and longer sustained penetration. Most sunscreens require application up to a half an hour before sun exposure to become effective, and also require frequent application in order to maintain protection. A solution is desired in order to make sunscreens effectively more quickly and for a longer duration, to prevent early burning and sun damage that may occur before the sunscreen becomes effective.
Topical skin preparation can also be beneficial prior to shaving. For conventional shaving with a safety razor or a straight razor, once the area to be shaved is wetted, a shaving soap or foam is applied in order to more fully hydrate the hairs. This procedure is followed both by males, when shaving the beard, and by women, when shaving legs, underarms, facial hair, or the bikini line. One disadvantage associated with shaving soaps and foams is that the hydration of the hairs is not complete, and thus they often do not lubricate well at the razor edge. The razor can tend to stick, leading to nicks, cuts, or skin irritation. In addition, the soaps or foams tend to desiccate the skin, and creams or emollients must often be applied after shaving to re-hydrate the skin.
Accordingly, in addition to the topical treatments discussed above, a shaving solution is desired that would provide a more effective and pleasant shaving method without requiring additional moisturizing subsequent to shaving.